1. Field of the Invention
This invention relates to novel end-functionalized poly(vinyl ethers). More particularly, this invention relates to novel poly(vinyl ether) amines having a hydroxy(oxypropylene) connecting group and their use in fuel compositions to prevent and control engine deposits.
2. Description of the Related Art
It is well known that automobile engines tend to form deposits on the surface of engine components, such as carburetor ports, throttle bodies, fuel injectors, intake ports and intake valves, due to the oxidation and polymerization of hydrocarbon fuel. These deposits, even when present in relatively minor amounts, often cause noticeable driveability problems, such as stalling and poor acceleration. Moreover, engine deposits can significantly increase an automobile's fuel consumption and production of exhaust pollutants. Therefore, the development of effective fuel detergents or "deposit control" additives to prevent or control such deposits is of considerable importance and numerous such materials are known in the art.
Deposit control additives, however, differ in their effectiveness for preventing or controlling deposits on various engine components. This is believed to be due primarily to the fact that each engine component has a different operating temperature and some deposit control additives are not sufficiently stable on the surface of certain engine components to perform their intended function. In this regard, deposits on intake valves are particularly difficult to control, since intake valve operating temperatures can exceed 300.degree. C. At such high temperatures, many fuel additives are too volatile to be effective, while others thermally decompose.
Therefore, it would be particularly desirable to provide effective deposit control additives which have improved thermal stability at normal engine intake valve operating temperatures and which further have a sufficient molecular weight so as to be nonvolatile at such temperatures. The present invention discloses a new class of poly(vinyl ether) amine fuel additives having such properties.
Polyether fuel additives are well known in the art. These prior art additives, however, have a poly(oxyalkylene) "backbone", i.e. the polyether portion of the molecule consists of repeating oxyalkylene units, i.e. [--CHR--CHR--O--.sub.x. In contrast, the fuel additives of the present invention have a vinyl ether polymer backbone consisting of repeating vinyl ether units, i.e. [--CHR--CR(OR)--].sub.x. U.S. Pat. No. 4,261,704, issued Apr. 14, 1981 to W. K. Langdon, for example, discloses a poly(oxyalkylene) polyamine prepared by first reacting a poly(oxyalkylene) polyol or a poly(oxyalkylene) glycol monoether with a halogen-containing compound, such as an epihalohydrin. The resulting halogenated ether is then aminated by reaction with a mono- or polyamine. The resulting mono- or polyamine derivatives are taught to be useful as intermediates for preparing cationic surfactants, cationic polymers and as fuel detergent additives.
Similar poly(oxyalkylene) polyamines, prepared using an epihalohydrin, are described in U.S. Pat. No. 4,281,199, issued Jul. 28, 1981 to W. K. Langdon. The compounds described in each of the aforementioned patents have a poly(oxyalkylene) backbone.
Other fuel additive compositions having a connecting group derived from an epihalohydrin are known. For example, U.S. Pat. No. 4,975,096, issued Dec. 4, 1990 to T. F. Buckley, discloses long chain aliphatic hydrocarbyl amines having a long chain aliphatic hydrocarbyl component and an amine component connected by an oxy-alkylene hydroxy connecting group. These compounds are taught to be useful as deposit control additives in fuel compositions and as dispersants in lubricating oil compositions. Similar multipurpose additives for hydrocarbon fuels and lubricating oils, prepared from substituted phenols, epichlorohydrin and amines, are described in U.S. Pat. No. 4,134,846, issued Jan. 16, 1979 to W. H. Machleder et al. The deposit control additives described in these patents do not have a polyether backbone.
End-functionalized poly(vinyl ethers) are also known in the art. For example, A. Verma et al. in Polymer Preprints, 1991, 32, 322, describe the synthesis and characterization of functionalized poly(butyl vinyl ether) oligomers having an aldehyde or a primary hydroxyl endgroup. These poly(vinyl ethers) are prepared by the living polymerization of butyl vinyl ether using a hydrogen iodide/zinc iodide initiating system. The polymerization reaction is terminated with aqueous potassium carbonate to form the aldehyde endgroup, which can subsequently be reduced to form the primary hydroxyl endgroup. Poly(vinyl ethers) having amine end-groups are also known. C. G. Cho et al., Polymer Preprints, 1987, 28, 356, describe the synthesis of amine-terminated poly(alkyl vinyl ethers) by quenching the living polymerization of alkyl vinyl ethers with p-methyl styrene and an amine. The resulting poly(alkyl vinyl ether) is covalently linked to the amine through a p-methyl styrenic unit. M. Miyamoto et al., Macromolecules, 1985, 18, 123, describe the synthesis of poly(vinyl ethers) having a terminal amine group by quenching the living polymerization reaction of vinyl ether monomers with aliphatic amines. The resulting poly(vinyl ether) amines have an .alpha.-amino ether endgroup. Similarly, M. Sawamoto et al., Polymer Bulletin, 1987, 18, 117, describes quenching vinyl ether polymerization reactions with anilines to form aniline-terminated poly(vinyl ethers).
Amine-terminated poly(isobutyl vinyl ethers) having a primary amine at the beginning of the vinyl ether polymer are described by T. Hashimoto et al. in J. Poly. Sci. Polym. Chem. Ed., 1990, 28, 1137. These poly(vinyl ethers) are prepared by initiating the living polymerization of isobutyl vinyl ether with 2-(vinyloxy)ethyl phthalimide. The phthalimide group is then removed with hydrazine to produce a poly(isobutyl vinyl ether) having a 2-aminoethyl ether moiety on the first vinyl ether unit of the polymer.
It has now been discovered that the thermal stability of polyether fuel additives can be substantially improved by replacing the poly(oxyalkylene) component of such additives with a poly(vinyl ether) component. The resulting poly(vinyl ether) amines are surprisingly effective for controlling fuel system deposits, particularly intake valve deposits.